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= High-level MAC Description =

The high-level MAC is responsible for inter-packet states that are not time critical. The state machine implemented by the high-level MAC has 6 states: {{{Idle}}}, {{{MPDU Tx}}}, {{{MPDU Rx}}}, {{{Ethernet Tx}}}, {{{Ethernet Rx}}}, and {{{Scheduled Event}}}.

[[Image(wiki:802.11/files:wlan_mac_cpu_high_overview.png, width=800)]]

== States ==

 * {{{Idle}}}: This state is the default state where no actions are performed by the high-level MAC. All other states return to {{{Idle}}} when completed.

 * {{{MPDU Tx}}}: This state handles the transmission of wireless MPDUs from a transmit queue.
  * Detailed description for Access Point: [wiki:./AP/MPDU_Tx MPDU Tx for AP]

 * {{{MPDU Rx}}}: This state handles the reception of wireless MPDUs.
  * Detailed description for Access Point: [wiki:./AP/MPDU_Rx MPDU Rx for AP]

 * {{{Ethernet Tx}}}: This state handles the transmission of wired Ethernet frames.
  * Detailed description for Access Point: [wiki:./AP/Ethernet_Tx Ethernet Tx for AP]

 * {{{Ethernet Rx}}}: This state handles the reception of wired Ethernet frames.
  * Detailed description for Access Point: [wiki:./AP/Ethernet_Rx Ethernet Rx for AP]

 * {{{Scheduled Event}}}: This state handles actions by the high-level MAC that are internally scheduled for times in the future.
  * Detailed description for Access Point: [wiki:./AP/Scheduled_Event Scheduled Event for AP]


== State Transitions ==

 * {{{Idle}}} → {{{MPDU Tx}}}: This transition occurs when two conditions are met: (a) The [wiki:../Low low-level MAC] has indicated that it is ready to receiver another packet for wireless transmission and (b) the transmit queue in the high-level MAC contains a packet that needs to be sent.

 * {{{Idle}}} → {{{MPDU Rx}}}: This transition occurs when the [wiki:../Low low-level MAC] has indicated that a reception has occurred with the following criteria: (a) the received packet is not a control packet (e.g. ACK, RTS, CTS) and (b) the received packet has a receiver address that is either a broadcast packet or a unicast packet whose address matches the MAC address of the node running this software.

 * {{{MPDU Rx}}} → {{{Ethernet Tx}}}: This transition occurs when a wireless MPDU data reception occurs that should be de-encapsulated and via Ethernet. Note: Unlike the {{{MPDU Tx}}} state, the {{{Ethernet Tx}}} state does not employ a queue. As such, it can be directly accessed from the {{{MPDU Rx}}} state without transitioning through {{{Idle}}}. The reason for this is that, even at the fastest 802.11g rates, wireless packets are much slower than wired packets. When receiving a wireless packet, there is enough time to directly transmit a wired packet without halting the next wireless reception. This is not the case for wired receptions.

 * {{{Idle}}} → {{{Ethernet Rx}}}: This transition occurs when any packet has been received by the Ethernet MAC on the board.

 * {{{Idle}}} → {{{Scheduled Event}}}: